Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well logging, profiling and monitoring of well conditions. Over the years, the detecting and monitoring of well conditions has become a more sophisticated and critical part of managing well operations.
Initial gathering of information relative to well and surrounding formation conditions may be obtained by running a logging tool in the well. The logging tool may be configured to acquire temperature, pressure, acidity and other well condition information. A map of the acquired information may be generated resulting in an overall profile of the well which may be of great value in subsequent monitoring and servicing of the well as noted below.
Servicing of the well is often performed by way of coiled tubing applications, particularly in the case of deviated wells. Coiled tubing applications involve the deployment of a string of narrow pipe through the well which is capable of delivering treatment fluids and carrying out a variety of downhole servicing applications. Of course, in order to effectively carry out any given application, the true position or location of the coiled tubing and associated tools should be known. Without such information, an otherwise effective application may be run at the wrong location in the well. By the same token, monitoring of a given application may also help to ensure that the application is effectively initiated and carried out to completion.
Generally, in order to establish the location of coiled tubing, a casing collar locator (CCL) is incorporated into the toolstring at the end of the coiled tubing. In order to provide location information, a CCL relies on the presence of intermittently dispersed casing collars of well casing defining the well. That is, a cased well generally consists of a series of equal length casing segments jointed to one another by casing collars. So, for example, where typical 30 ft. casing segments are employed in defining the inner wall of a cased well, a casing collar may be found every 30 feet throughout the well. In this manner, casing collar detection may be acquired as the application tool is advanced through the well. Thus, accurate positioning of the application tool may be ensured. CCL's are generally available in flow-through configurations and thus, work particularly well with coiled tubing applications.
Unfortunately, CCL's may only be utilized in situations where the well is cased. That is, where no casing or casing collars are present, such as the circumstance of an open-hole well, CCL's are unable to provide any location information. Furthermore, while location in terms of well depth of a cased well may be established with a CCL, other types of location information may not be determined with such a locator. For example, often times the well architecture includes a variety of downhole offshoots or ‘lateral legs’ which branch off from the main vertical channel of the well. When this is the situation, not even casing of the well and lateral legs would allow a CCL to provide information relative to the particular lateral leg within which the coiled tubing and toolstring are disposed. That is, while sometimes a decent indicator of well depth, the CCL is unable to provide any more specific information as to the whereabouts of the coiled tubing and toolstring.
In addition to the above noted deficiencies of a CCL for open-hole or lateral leg applications, the CCL often fails to provide adequate location information even in cased wells of fairly unsophisticated architecture. For example, accuracy of the CCL requires the detection of every casing collar traversed. That is, with the above casing example in mind, the accuracy of the depth information arising from the CCL will be off by 30 feet for every collar the CCL fails to detect. Unfortunately, failure to detect a collar is not an uncommon occurrence, particularly as wells become deeper and deeper with an ever increasing number of casing collars to be detected. As such, keeping with the noted casing example, the odds of a coiled tubing application being directed to a downhole location that is 30, 60, or 90 feet off target is a distinct possibility. Thus, an ineffective clean out, misapplied fracturing, or other erroneous coiled tubing application may be likely.
As noted above, static well location information, as such relates to the coiled tubing, may play a significant role in the effectiveness of the coiled tubing application to be carried out. As also alluded to, dynamic well condition information, relative to the coiled tubing application, may also be quite beneficial. For example, monitoring a rate or degree of a clean out may avoid significant expenses associated with having to re-run the application due to ineffectiveness or incompleteness. Unfortunately, however, a coiled tubing tool equipped for static well detections such as a CCL is unable to provide such dynamic well condition information.